The reliability, and thus the safety, of automotive hydraulic brake systems depends to a significant extent upon the capability to purge such systems of air. This purging or bleeding air from the systems involves filling a system from the driver-operated master cylinder to the brake-actuating wheel cylinders with hydraulic brake fluid to the exclusion of air. In a proper and professional bleeding operation, brake fluid is introduced under pressure (from a tank or other source) to the master cylinder to flood the system with fluid and thus to drive air from the system at vent valves located at the various wheel cylinders.
Modern automotive brake systems are "dual". That is, a master cylinder having a tank or reservoir is provided with two inlets connected to the reservoir. In normal operation, when the vehicle driver depresses the foot pedal to actuate the master cylinder fluid is forced through both of the dual systems to all four wheel cylinders to perform the braking operation. In the event of rupture or other failure in one of the dual systems, braking can still take place because the master cylinder will supply the remaining or sound system supplying two of the wheel cylinders.
Heretofore, in bleeding brake systems it has been the practice to remove the cover of the master cylinder reservoir, to then make certain that the reservoir is at least partially filled to provide a body of fluid over the master cylinder inlets, then to provide a substitute cover or plate over the reservoir having a tubular appendage whose lower end would be submerged in the fluid in the reservoir, and then to supply brake fluid from a source under pressure to such appendage and thus to the inlets for the dual brake systems.
Recent master cylinder design changes, for various reasons, have brought about non-uniformity in the configuration of the master cylinder reservoirs. As a result, the brake bleeding plate with its tubular extension for the reservoir cannot be depended upon for use in bleeding all brake systems.
Accordingly, and in meeting this problem, it is the general object of the present invention to provide a harness which is adaptable to most, and perhaps all, master cylinder reservoirs for introducing brake fluid under pressure in the system bleeding operation.